RGB Bildlage-Shifter (sync shifter).

[KillingBeans]

I'm thinking about building a SCART RGB switch box using some HC4052 chips. It should be fairly easy to do.
My CRT shifts the RGB picture horizontally. It's very irritating. So I'd like to add someting to my switch box that lets me shift the picture to the correct position. This circuit seems like an obvious choice:

http://playoffline.wordpress.com/cable/rgbshifter/

The people who designed this do a really good job at telling how to build it and how to use it, but they don't really cover any of the theory on how the damn thing works. That kinda bugs my. I like to know how things work before I start building them.

So... I've boiled it down to this:



I understand how the NAND gate separates the H-sync, how the two multivibrator introduces the necessary delays on the H-sync and how the AND gate combines the H-sync and V-sync into C-sync again.

But the thing that has me puzzled is the alternative circuit that the switch can activate. Can any of you guys explain it's function?

The build guide mentions that it's only necessary to use the alternative circuit on certain monitors that otherwise will show distortions in the top part of the picture. Am I right to assume that the monitors in question are the flat screen types and others of the kind that puts the signals through digital processing and therefore reacts critically on the timing conditions?

If I only intend to use the shifter on normal "analog" CRTs, would it render the alternative circuit useless?

EDIT: No wait, I've been looking at the NAND as if it was an X-NOR. The NAND actually spits out inverted H-sync? Now I understand absolutely nothing 

[KillingBeans]

I guess there's only one thing to do. Draw a pile of logic waveforms and hope it doesn't drive me crazy to look at them